There may be a difference between a 'sticker' and a 'decal'. This is a sticker IMO. A clean dry surface is required. I'd also assume that you may want to remove any wax first with ammonia before application and once it's on, it's on. YB and others would know more about this and I don't know if anyone actually has theirs yet but I don't think moisture of any kind is a good idea unless you don't want it to stick.